In recent years, driving assistance apparatuses (called “driving assistance applications” hereinafter) that assist in the driving of a moving vehicle are being developed. For example, lane keep apparatuses that automatically steer or assist in driving so that vehicles travel along a road, lane departure prevention apparatuses that assist in driving by preventing vehicles from departing from their lanes, emergency avoidance apparatuses that automatically steer vehicles in order to avoid obstructions on the traveled road surface, and so on are being developed.
Request signals outputted from a driving assistance application such as a lane keep apparatus, a lane departure prevention apparatus, or an emergency avoidance apparatus (for example, a signal indicating a target lateral acceleration) are inputted into a lateral motion control apparatus that controls the amount of lateral motion (for example, the yaw rate) of the vehicle. Control signals are outputted from the control apparatus to a control target such as an actuator. The lateral motion of the vehicle is controlled as a result of the control target being controlled based on the control signals.
In the case where a driver has performed steering operations while the lateral motion of the vehicle is being controlled by the lateral motion control apparatus based on a request signal outputted from a driving assistance application (such interventional steering performed by the driver will be called “overriding”), the lateral motion control performed by the lateral motion control apparatus is stopped in order to give priority to the steering operations performed by the driver.
JP2003-81115A discloses a lane departure prevention apparatus that determines that an override is occurring in the case where a steering angle θ is greater than or equal to a set steering angle θ1 after a set time T1 has passed after a steering angle velocity absolute value |dθ| becoming greater than or equal to a set threshold value dθ1. According to this apparatus, it is determined that an override is not occurring if the steering angle θ is less than the set steering angle θ1 after T1 has passed even if the steering angle velocity absolute value |dθ| is greater than or equal to the threshold value dθ1, which prevents the control of the lateral motion amount of the vehicle from being stopped when the steering angle velocity has temporarily exceeded the set threshold value due to the influence of disturbances or the like. Furthermore, JP2003-81115A also discloses a lane departure response apparatus that changes the set threshold value used in the determination as to whether or not an override is occurring based on the position of the vehicle in a lane, the curvature factor during a turn, and so on.